1. Field of the Invention
The present invention relates to a display device having a functional element formed on a flexible substrate. More specifically, the present invention relates to a display device preferably used in a passive matrix drive mode.
2. Description of the Related Art
As a next-generation display or a next-generation device, paper-like flexible displays and flexible lighting have begun to receive considerable attention, which displays or devices are realized by laminating a transparent electrode, an optical functional layer including an organic light emitting element or a liquid crystal element, and a back electrode on a transparent and flexible substrate, and forming a plurality of display pixels. These flexible displays are thin, lightweight, and easily portable, and can be folded when not used and unfolded when used, or suchlike. To achieve a flexible display, a flexible substrate, robust display pixels, durability of the display, miniaturization of the display and the like, are required.
Solutions for accomplishing miniaturization and reduction of weight are disclosed in Japanese Patent Application Laid-Open (JP-A) Nos. 2002-82627 and 2003-17245, but the problems have not been solved sufficiently thus far. As a driving system of a flexible display, two methods have been studied, that is, a passive matrix drive mode and an active matrix drive mode. However, since it is generally difficult to manufacture a flexible thin film transistor (TFT) that exhibits sufficient performance on a flexible substrate such as polyethylene naphthalate (PEN), the passive matrix drive mode is expected to be an effective driving mode. However, in the case of control by the passive matrix drive mode, the amount of wiring to be connected to an external drive circuit is larger than when the active matrix drive mode is used. Hence, dead space is increased. Accordingly, a technique for reducing the space taken up by wiring is required.
Further, a display unit such as a display is constituted by a collection of multiple display pixels present on a region formed by two electrodes, that is, an anode and a cathode, disposed in intersecting directions and an optical functional layer disposed between the two electrodes. Since two electrodes are disposed in intersecting directions, in the case of a rectangular panel, for example, electrodes are respectively drawn out from two adjacent sides, connected to a drive unit using a flexible printed circuit (FPC) or the like, and controlled. The passive matrix drive mode is an effective driving method for a flexible display, but it requires a large amount of connecting wiring for driving, and a large space is required for the wiring.
To realize a flexible display, it is essential to minimize the space occupied by constituents of the display other than the display unit, and it is important to house the wiring portions in a smaller space.